The Concept of Lamina–Pedicle Perpendicularity: Part 2: Thoracic Spine

ABSTRACT

Methods@#This was a retrospective study on the computed tomography (CT) chest scans of patients with no spinal pathologies. The ILL–PA, superior and inferior safe angles of the pedicle screw trajectories, and the exit zone of the screw perpendicular to the ILL were reviewed by two observers via three-dimensional multiplanar reconstruction mode of the Horos DICOM software (https// horosproject.org/). @*Results@#The CT chest images of 30 consecutive patients (20 males and 10 females) with a mean age of 49.87±15.48 years (range, 24–74 years) were evaluated. The mean ILL–PA angle was almost orthogonal for all levels. This angle ranged between 86.21°±3.01° at D5 and 90.59°±2.72° at D10. The safety zones of the sagittal inclination of the pedicle screws were demonstrated. The results revealed that the least safe angle was when the screw was directed cranially along the middle part of the pedicle between 4.43°±0.75° at D8 and 6.94°±1.19° at D11. @*Conclusions@#The results of this study confirmed the ILL–PA angle perpendicularity in the thoracic spine at all levels. The ILL is a useful guide for pedicle screw sagittal inclination.